AU704191B2 - A gas seal embracing the distributor, the twin-rolls and the side wall abutments of a twin-roll continuous caster - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT 9 9 9 99 9 9*9 Applicant(s): ISHIKAWAJIMA-HARIMA HEAVY INDUSTRIES COMPANY

LIMITED

BHP STEEL (JLA) PTY LTD 20 A.C.N. 000 011 058 Invention Title: A GAS SEAL EMBRACING THE DISTRIBUTOR, THE TWIN-ROLLS AND THE SIDE WALL ABUTMENTS OF A TWIN-ROLL CONTINUOUS

CASTER.

The following statement is a full description of this invention, including the best method of performing it known to me/us: \\melb01\homeS\Ananos\Keep\Spec1\55871-96.3.doc 9/02/99 2 A GAS SEAL EMBRACING THE DISTRIBUTOR, THE TWIN-ROLLS

AND

THE SIDE WALL ABUTMENTS OF A TWIN-ROLL CONTINUOUS

CASTER.

The present invention relates to a twin roll continuous caster.

In a twin roll continuous caster, between upper surfaces of opposite ends of a pair of horizontal and parallel rolls, seal plates called side weirs are abutted to confine a melt pool above a nip between the rolls.

Molten metal is supplied to the pool and is solidified on the roll surfaces. The rolls are rotated under this condition so that solidified shells formed on the roll surfaces are pulled down together to directly cast a thin strip.

15 Figs. 8 to 10 illustrate a conventional twin roll continuous caster. Between upper surfaces of opposite ends of a pair of horizontal and parallel xolls 1 and 2, seal plates called side weirs 3 are abutted to confine a melt pool 4 above a nip between the rolls 1 and 2.

20 The rolls 1 and 2 used are capable of being internally cooled so as to facilitate the solidification of molten metal 5. Alternatively, rolls are used which are made of a material such as copper with high thermal conductivity.

The side weirs 3 have their upper surfaces 6 positioned higher than an upper common tangential line 7 on the rolls 1 and 2 and have their width 8 shorter than a distance 9 between axes of the rolls 1 and 2.

In order to supply the molten metal 5 to the pool 4, a distributor 10 is arranged above the pool 4 and has a 30 pouring nozzle 11 protruded from the distributor 10 to the pool 4.

Further, a sealed chamber 12 is provided under the distributor 10 to surround the pool 4.

The chamber 12 is partitioned into upper and lower portions by a straightening plate 13 such as punched plate and is formed with inert gas inlets 15 on a front end wall 14 of the chamber 12 and at positions above the plate \\melbO1\homeS\Ananos\Kep\Sp. i\55871- 9 6 .3.doc 9/02/99 3 13 so as to supply inert gas 16 such as nitrogen or argon gas to the chamber.

Further, as shown in Fig. 9, gas seals 19 each in the form of thin plate are mounted between lower ends 18 of left and right side walls 17 of the chamber 12 and the barrels of the rolls 1 and 2, respectively. As shown in Fig. 10, gas seals 21 each in the form of thin plate are mounted between lower ends 20 of front and rear end walls 14 of the chamber 12 and the upper surfaces 6 of the side weirs 3, respectively.

Reference numeral 22 denotes solidified shells on the surfaces of rolls 1 and 2; and 23, a produced thin strip with thickness in the order of several millimetres.

The molten metal 5 in the distributor 10 is 15 supplied through the pouring nozzle 11 into the pool 4 confined by the upper surfaces of the rolls 1 and 2 and the S.9 s:d weirs 3 i soldified on the surfaces of the rolls 1 and 2.

In this condition, the rolls 1 and 2 are rotated 20 in directions indicated by arrows in the figure so that the solidified shells 22 on the surfaces of the rolls 1 and 2 are pulled down together to directly cast the thin strip 23.

In this case, if air contacts the molten metal 25 in the pool 4, the molten metal 5 would be oxidised, leading to deterioration of the quality of the strip 23 9 produced. To overcome this, the sealed chamber 12 is provided between the distributor 10 and the pool 4 and the inert gas 16 such as nitrogen or argon gas is supplied f 30 through the inert gas inlets 15 to the chamber 12 to prevent the molten metal 5 in the pool 4 from being oxidised and produce the strip 23 with high quality.

In this connection, as shown in Fig. 9, the gas seals 19 seal between the lower ends 18 of the side walls 17 of the chamber 12 and the barrels of the rolls 1 and 2, respectively.

Further, as shown in Fig. 10, the gas seals 21 imelb0'\home$\Ananos\Kee\Speci\55871-96.3 .doc 9/02/99 a 4 Further, as shown in Fig. 10, the gas seals 21 seal between the lower ends 20 of the end walls 14 of the chamber 12 and the upper surfaces 6 of the side weirs 3 respectively.

However, the above-mentioned conventional twin roll continuous caster has a below-mentioned problem.

Since the upper surfaces 6 of the side weirs 3 are positioned higher than the upper common tangential line 7 on the rolls 1 and 2 and the width 8 of the side weirs 3 is shorter than the distance 9 between the axes of the rolls 1 and 2, zones or portions shown by A in Fig. 8, corners between the walls 14 and 17 of the chamber 12 are not sealed.

Therefore, air may enter into the chamber 12 through the zones A to oxidise the molten metal 5 in the pool 4, leading to the deterioration of the quality of the strip 23 produced. To prevent such oxidation of the molten 4" metal 5, a large quantity of inert gas 16 must be supplied to the chamber 12, which may in turn lead to increase of 20 production cost.

In view of the above, the present invention has its object to provide a twin roll continuous caster which can ameliorate sealing between the sealed chamber and the rolls and side weirs.

25 To attain the above object, a twin roll continuous caster of the present invention comprises a pair of horizontal and parallel rolls, side weirs abutted between upper surfaces of opposite ends of said rolls to confine a melt pool above a nip between the rolls, a 30 distributor above the pool for supplying molten metal to the pool and a sealed chamber under the distributor to surround the pool and supplied with inert gas, characterised in that the side weirs have upper surfaces positioned at a height equal to that of an upper common tangential line on said rolls and have width longer than a distance between axes of the rolls, that left and right side walls of the sealed chamber are provided by gas seal 8 71-96.3.doc 9/02/99 rplates which extend longitudinally of the rolls to reach outer surface positions of the side weirs and whose lower ends are contacted with barrels of the rolls and the upper surfaces of the side weirs at positions of contact points between said rolls and the upper common tangential lines and that front and rear end wall members of the sealed chamber are formed at their lower ends with horizontal portions having the same length as the distance between the axes of the rolls and closely fittable to the upper surfaces of the side weirs.

In this case, the gas seal plate may comprise a plurality of sheets having at their lower portions a plurality of slits, said sheets being overlapped such that the slits are deviated in the longitudinal direction of the 15 rolls.

99, Further, a heat-resistant, elastically deformable seal, which comprises a plurality of sheet members overlapped and made of heat-resistant metal fibers, may be *intervened between the horizontal portion of the lower end 20 of the end wall member of the sealed chamber and the upper surface of the side weir.

Operation of the present invention is as follows: The molten metal from the distributor is supplied via the pouring nozzle to the melt pool confined by the 25 upper surfaces of the rolls and the side weirs and is solidified on the roll surfaces.

The rolls are rotated in this condition so that the solidified shells formed on the roll surfaces are pulled down together to directly cast the thin strip.

30 In this case, if air contacts the molten metal in the pool, the molten metal would be oxidised, leading to deterioration of the quality of the strip produced. To overcome this, the sealed chamber is provided between the distributor and the pool and the inert gas such as nitrogen or argon gas is supplied through the inert gas inlets to the chamber, thereby preventing the molten metal in the pool from being oxidised.

71-96.3.,do 9/02/99 r 6 For this purpose, according to the present invention, left and right side walls of the sealed chamber are provided by gas seal plates each of which comprises a plurality of sheets extending longitudinally of the rolls and having at their lower portions a plurality of slits, said sheets being overlapped such that the slits are deviated in the longitudinal direction of the rolls. The gas seal plates are contacted at their lower ends with the rolls at positions of contact points between the rolls and the upper common tangential lines.

This causes the lower ends of the gas seal plates to have flexibility. Owing to the flexibility, the lower ends of the gas seal plates are closely fitted to the surfaces of the rotating rolls under a given pressure to 15 prevent leakage of the inert gas and prevent the roll surfaces from being damaged by the lower ends of the gas o seal plates.

Since the sheets are overlapped with their slits being deviated longitudinally of the rolls, leakage of the 20 inert gas through the slits is substantially prevented.

The upper surfaces of the side weirs are positioned at the same height as the common tangential line on the rolls and the width of the side weirs is made longer than the distance between the axes of the rolls. The "25 longitudinal ends of the gas seal plates have extensions reaching the outer surface positions of the side weirs and the lower ends of the gas seal plates are contacted with the barrels of the rolls and the upper surface of the side weirs at positions of contact points with the common i 30 tangential lines. As a result, the lower portions of the sealed chamber, the lower ends of the gas seal plates and the horizontal portions of the lower ends of the end wall members are on the same horizontal plane to form a continuous and non-interrupted rectangle. Thus, substantially no gaps are formed in the lower portion of the sealed chamber, in particular, at the corners of the chamber. As a result, substantial sealing can be provided.

H:\Ananos\Kep\speci\55871-96.3.dc 9/02/99 7 Owing to the above-mentioned sealing structure where the lower portions of the sealed chamber, the lower ends of the gas seal plates and the horizontal portions of the lower ends of the end wall members are on the same horizontal plane, the sealing condition as described above can be maintained even when the distributor or the sealed chamber is thermally expanded longitudinally with respect to the rolls and the side weirs.

Similarly, owing to the above-mentioned sealing structure where the lower portions of the sealing chamber, the lower ends of the gas seal plates and the horizontal portions of the lower ends of the end wall members are positioned on the same horizontal plane and the lower ends of the gas seal plates are contacted with the 15 rolls at positions of contact points with the common tangential lines, at the positions of highest points on the rolls and having minimal change in height due to positional deviation with respect to the rolls. As a result, even when the nip between the rolls is changed more or less to adjust the thickness of the thin strip to be produced, the above-mentioned sealing condition can be maintained as it is.

Further, heat-resistant elastically deformable o° 0seals, each of which comprises a plurality of overlapped 25 sheet members made of heat-resistant metal fibers, are intervened between the horizontal portions of the lower e* ends of the front and rear end wall members of the sealed chamber and the upper surfaces of the side weirs. As a result, even when the horizontal portions of the lower ends 30 of the end wall members and/or the upper surfaces of the side weirs may be thermally deformed or have surface roughness due to heat from the molten metal, the heatresistant, elastically deformable seals can follow such thermal deformation or surface roughness of the lower ends of the end wall members and/or the upper surfaces of the side weirs, substantially preventing leakage of the inert S gas through gaps which otherwise may be produced between H:\Ananos\Keep\speci\55%71-96.3.doc 9/02/99 8 them.

As described above, oxidation of the molten metal is effectively minimised or prevented and thin strip with high quality can be obtained. Also, the required quantity of the inert gas is extensively reduced, which prevents increase of production cost.

An embodiment of the present invention will now be described in conjunction with the drawings.

BRIEF DESCRIPTION Fig. 1 Fig.

Fig. a

S.

S

4 9* Fig. 4 Fig.

Fig.

Fig.

OF THE DRAWINGS A schematic front view of an embodiment of the invention.

A side view of Fig. 1.

A view same as Fig. 1 with the side weir and the end wall member removed.

A view same as Fig. 2 with the gas seal plate removed.

A side view of the gas seal plate.

A partial enlarged view of Fig. A partial enlarged view of the heatresistant, elastically deformable seal.

A partially cutaway schematic front view of a conventional machine.

A partial enlarged view of Fig. 8.

A view looking in the direction of Arrows X in Fig. 8.

Fig. 8 Fig.

Fig.

t9 30 Figs. 1 to 7 represent a preferred embodiment of the present invention.

Between upper surfaces of opposite ends of a pair of horizontal and parallel rolls 24 and 25, seal plates called side weirs 26 are abutted to confine a melt pool 27 above a nip between the rolls 24 and The rolls 24 and 25 used are capable of being internally cooled so as to facilitate the solidification of H:\Ananos\Keep\Specl\55871-96.3.doc 9/02/99 I I 9 a molten metal 28.

Alternatively, rolls are used which are made of a material such as copper with high thermal conductivity.

The rolls 24 and 25 are supported on a base 31 via shaft supports 30 with bearings 29, respectively, and are driven by a drive unit (not shown).

The side weirs 26 have upper surfaces 64 at the same height as an upper common tangential line 32 on the rolls 24 and 25 and have width 33 longer than a distance 34 between axes of the rolls 24 and Each of the side weirs 26 is urged by a rod-like pusher 37 which extends in a longitudinal direction 36 of the rolls 24 and 25 and which is mounted on a connecting member 35 which in turn interconnects upper ends of the J 15 supports The pusher 37 is formed at its outer surface with .6.

a thread 38 and is position-adjustably screwed into a screw hole 39 on the connecting member 35. The pusher has a projection 40 accomodated in its tip for protrusion in the 2 20 longitudinal direction 36 and a spring 41 for biasing the projection 40 toward the side weir 26.

In order to supply the molten metal 28 to the pool 27, a distributor 42 is provided above the pool 27 and has a pouring nozzle 43 protruded from the distributor 42 25 to the pool 27.

The distributor 42 has brackets 44 which are horizontally protruded from front and rear surfaces of the distributor respectively, and into which threaded shafts 47 are screwed each of which in turn is on a top of a support 30 member 46 extending from the base 31 in a vertical .direction 45. Thus, the distributor is position-adjustably supported via nuts 48 screwed on the shafts 47.

Under the distributor 42, a sealed chamber 49 is provided to surround the melt pool 27. The chamber 49 is formed with inert gas inlets 50 on its front end wall member 66 so as to supply inert gas 51 such as nitrogen or -argon gas to the chamber 49.

H:\Anano\Keep\Speci\55871-96.3.doc 9/02/99 10 Left and right side walls of the chamber 49 are provided by gas seal plates 52 extending in the longitudinal direction 36 of the rolls 24 and The gas seal plate 52 comprises, as shown in Figs. 5 and 6, a plurality of sheets 54 made of, eg., stainless steel, with dozens of microns in thickness and having at their lower ends a plurality of equidistantly spaced slits 53 extending in the vertical direction 45 so as to have flexibility at the lower ends, said sheet materials 54 being overlapped such that the slits 53 of the sheets are deviated in the longitudinal direction 36 of the rolls 24 and The gas seal plate 52 is contacted at its lower end with contact points 55 where the rolls 24 and 25 meet 15 the common tangential lines 32, along the longitudinal direction 36, and is fixed to an inclined side portion 61 of the distributor 42, using a mounting plate 59, a spacer and bolts 57 and 58, so as to be held generally °at an angle 56 of approximately 30 degrees to the vertical.

*o 20 Further, the gas seal plate 52 has extensions 63 which reach opposite outer surface positions 62 of the side weirs 26 in the longitudinal direction 36 and which are contacted at their lower ends with upper surfaces 64 of the side weirs 26.

25 In Fig. 5, reference numeral 65 represents bolt holes formed on the gas seal plate 52.

Each of front and rear end wall members 66 of the sealed chamber 49 has at its lower sides inclined portions 73 to which the gas seal plates 52 are closely fitted. The 30 end wall members 66 have at their lower ends horizontal portions 74 which have a length equal to the distance 34 between the axes of the rolls 24 and 25 and which are closely fittable to the upper surfaces 64 of the side weirs 26.

Intervened between the horizontal portions 74 on the lower ends of the front and rear end wall members 66 of the sealed chamber 49 and the upper surfaces 64 of the side H:\Annanos\Keep\spei\S5871-96.3.doc 9/02/99 11 weirs 26 are heat-resistant, elastically deformable seals 69 each of which comprises a plurality of overlapped sheet members 68 made of ribbon-likely interwoven, heat-resistant metal fibers 67 such as stainless steel fibers.

Reference numeral 70 denotes bolts which fix the end wall members 66 to the front and rear surfaces of the distributor 42.

Reference numeral 71 denotes solidified shells on the surfaces of the rolls 24 and 25; and 72, a produced thin strip with thickness in the order of several millimetres.

Next, mode of operation will be described.

The molten metal 28 from the distributor 42 is supplied via the pouring nozzle 43 to the melt pool 27 I 15 between the side weirs 26 and the upper surfaces of the rolls 24 and 25 and is solidified on the surfaces of the

S.•

rolls 24 and In this condition, the rolls 24 and 25 are 9 •rotated in directions shown by arrows in the figures, using a drive unit (not shown). The solidified shells 71 formed on the surfaces of the rolls 24 and 25 are pulled down together to directly cast the thin strip 72.

In this case, if air contacts the molten metal 28 ee* in the pool 27, the molten metal 28 would be oxidised, 25 leading to deterioration of the quality of the strip 72 produced. To overcome this, the sealed chamber 49 is provided between the distributor 42 and the pool 27 and the inert gas 51 such as nitrogen or argon gas is supplied via the inert gas inlets 50 to the chamber 49. As a result, 30 oxidation of the molten metal 28 in the pool 27 is substantially prevented.

For this. purpose, the side walls of the sealed chamber 49 are provided by the gas seal plates 52 each of which comprises a plurality of sheets 54 made of metal such as stainless steel and with thickness of dozens of microns and extending in the longitudinal direction 36 of the rolls 24 and 25, the sheets having at their lower ends a H:\Ananos\Keep\Specl\55871-96.3.doc 9/02/99 12 plurality of slits extending in the vertical direction and overlapped such that the slits 53 are deviated in the longitudinal direction of the rolls 24 and 25. The gas seal plates 52 are contacted at their lower ends with the rolls at positions of contact points 55 between said rolls 24 and 25 and the upper common tangential lines 32.

As a result, the gas seal plates 52 have flexibility at their lower ends, which flexibility will cause the lower ends of the gas seal plates 52 to be closely fitted with the surfaces of the rotating rolls 24 and 25 under given pressure. This will substantially prevent leakage of the inert gas 51 and also substantially prevents damage of the surfaces of the rolls 24 and 25 by the lower ends of the gas seal plates 52.

15 Since the sheets 54 are overlapped with the slits 53 being deviated in the longitudinal direction 36 of the o* rolls 24 and 25, leakage of the inert gas 51 through the slits 53 is substantially prevented.

eThe upper surfaces 64 of the side weirs 26 are positioned to the same height as the upper common tangential line 32 of the rolls 24 and 25 and the width 33 of the side weirs 26 is longer than the distance 34 between the axes of the rolls 24 and 25. Also, the gas seal plates *6 52 have, at their ends in the longitudinal direction 36, 25 extensions 63 reaching the outer surface positions 62 of the side weir 26 and are contacted at their lower ends with p. the barrels of rolls 24 and 25 and the upper surfaces 64 of the side weirs 26 at positions of the contact points with the upper common tangential lines 32. As a result, 30 the lower portions of the sealed chamber 49, the lower ends of the gas seal plate 52 and the horizontal portions 74 of the lower ends of the end wall members 66 are on the same horizontal plane to define a continuous and non-interrupted rectangle. Thus, it is possible to provide substantially no gaps on the lower portions of the sealed chamber 49, in particular, at the corners. As a S result, substantial sealing can be obtained.

H:\Ar..os\Keep\Spe-i55871-96.3.d-e 9/02/99 13 By the above sealing structure in which the lower portions of the sealed chamber 49, the lower ends of the gas seal plates 52 and the horizontal portions 74 of the lower ends of the end wall members 66 are on the same horizontal plane, the above sealing condition can be maintained even when the distributor 42 and/or the sealed chamber 49 are thermally expanded in the longitudinal direction 36 with respect to the rolls 24 and 25 and/or the side weirs 26.

Similarly, by the above sealing structure in which the lower portions of the sealed chamber 49, i.e., the lower ends of the gas seal plates 52 and the horizontal portions 74 of the lower ends of the end wall members 66 are on the same horizontal plane and the gas seal plates 52 15 are contacted at their lower ends with the rolls at I: positions of contact points of the rolls 24 and 25 with the upper common tangential lines 32, at the positions of

V.

highest point on the rolls 24 and 25 where the change in height due to positional deviation with respect to the 20 rolls 24 and 25 becomes minimal, the above sealing condition can be maintained even when the nip between the rolls 24 and 25 is changed more or less to change thickness 4. of the thin strip 72 to be produced.

Further, heat-resistant, elastically deformable 25 seals 69, each of which comprises a plurality of overlapped sheet members 68 made of ribbon-likely interwoven, heatresistant metal fibers 67 such as stainless steel fibers, are intervened between the horizontal portions 74 of the lower ends of the front and rear end wall members 66 of the 30 sealed chamber 49 and the upper surfaces 64 of the side weirs 26. Therefore, even when the horizontal portions 74 of the lower ends of the end wall members 66 and/or the upper surfaces 64 of the side weirs 26 are thermally deformed or have surface roughness due to heat from the molten metal 28, the heat-resistant elastically deformable seals 69 follow thermal deformation or surface roughness of Rthe lower ends of the end wall members 66 and/or of the H:\Ananos\Keep\Speci\55871-96.3.doc 9/02/99 I

I

14 upper surfaces 64 of the side weirs 26 and are deformed, which substantially prevents leakage of the inert gas 51 through gaps which may otherwise be produced between them.

As described above, oxidation of the molten metal 28 can be effectively minimised or prevented and production of the thin strip 72 with good quality is assured. Also, the required quantity of the inert gas 51 is extensively reduced, which prevents increase of production cost.

It is needless to say that the present invention is not limited to the above-mentioned embodiment and that various changes and modifications may be made without departing from the scope and the spirit of the present invention.

As described above, the twin roll continuous .15 caster of the invention provides excellent sealing between the sealed chamber and the rolls and side weirs.

6 0 49 H: \AnanoS\Keepspecl\558771- .3.doc 9/02/99

Claims (4)

1. A twin roll continuous caster comprising a pair of horizontal and parallel rolls, side weirs abutted between upper surfaces of opposite ends of said rolls to confine a melt pool above a nip between the rolls, a distributor above the pool for supplying molten metal to the pool and a sealed chamber under the distributor to surround the pool and supplied with inert gas, wherein the side weirs have upper surfaces positioned at a height equal to that of an upper common tangential line on said rolls and have width longer than a distance between axes of the rolls, that left and right side walls of the sealed chamber are provided by gas seal plates which extend longitudinally 15 of the rolls to reach outer surface positions of the side a" weirs and whose lower ends are contacted with barrels of the rolls and the upper surfaces of the side weirs at *positions of contact points between said rolls and the upper common tangential lines and that front and rear end 20 wall members of the sealed chamber are formed at their lower ends with horizontal portions having the same length as the distance between the axes of the rolls and closely fittable to the upper surfaces of the side weirs. .9 25

2. A twin roll continuous caster as claimed in claim 1, wherein the gas seal plate comprises a plurality of sheets having at their lower portions a plurality of slits, said sheet materials being overlapped such that the slits are deviated in the longitudinal direction of the rolls.

3. A twin roll continuous caster as claimed in claim 2, wherein the slits extend substantially vertically.

4. A twin roll continuous caster as claimed in any one of claims 1 to 3, wherein intervened between the horizontal portion of the lower end of the end wall member of the sealed chamber and the upper surface of the side \\melbOl\hone$\Anos\Keep\spci\5587196.3.doc 9/02/99 16 weir is a heat-resistant, elastically deformable seal which comprises a plurality of sheet members overlapped and made of heat-resistant metal fibers. Dated this 9th day of February 1999 ISHIKAWAJIMA-HAIMI HEAVY INDUSTRIES COMPANY LIMITED and BHP STEEL (JLA) PTY LTD By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia o*0 04 000 00 0* 00 *0e 0600 *00 \\Melb~i\hIOne\nano3\Keep\Speci\ 5 8 7 l96. 3 .doc 9/02/99